Some phones (e.g. Samsung D500, Motorola MPx220, and possibly some
other Windows Mobile models) don't return any services if you ask them
for the public browse group.  You notice this, when "sdptool browse
xx:xx:xx:xx:xx:xx" returns immediately, without any output.

It turns out that the Windows XP Bluetooth browser asks for
L2CAP_UUID, which *does* work for all the phones I've tested.

So I've made this simple patch, that adds a `-l' or `--l2cap' command
line option to sdptool, to use the L2CAP_UUID for browsing, instead of
PUBLIC_BROWSE_GROUP.